Patients with COPD had comparable IL-33 levels regardless of disease severity (GOLD 2: 0 pg/mL, IQR 0–99.12 vs. GOLD 3: 0 pg/mL, IQR 0–74.67 vs. GOLD 4: 0 pg/mL, IQR 0–0.55, p = 0.185, Figure 1D). Here, IL33 is linked to chronic obstructive pulmonary disease.